According to current practice in the electronics industry, various electrical metal components, such as contact pins, are manufactured in strip form. These strips are typically separated into individual components as one of the last operations prior to assembling the components into a larger piece of electrical apparatus.
One type of operation which conveniently may be applied while the components are still in the form of a strip, is an electrolytic treating operation, such as etching or plating. In a plating operation, for example, the entire strip is cathodically coupled into a plating circuit, and the strip is moved lengthwise through an electrolytic plating bath past a plating anode.
Often, such an electrolytic treating operation is desirably applied to only portions of the components. Various ways of masking are known. It is, for example, possible to paint or screen print a selective masking layer directly onto predetermined portions of the strip prior to the electrolytic treatment. Such masking layer is then removed after the treatment. If the shape of the components in the strip is intricate, applying such a mask is often not feasible.
Also, a pair of endless belts, positioned for parallel, adjacent travel for one common portion of their path, have been used to mask a desired portion of articles. Such a masking operation is, for example, shown in U.S. Pat. No. 4,186,062 to Eidschun. The patent discloses the belts as a conveying and masking instrumentality for a plurality of printed wiring boards. The boards, sandwiched between the belts, enter a plating cell. The resulting plated layer is terminated at a demarcation line defined by the edges of the belts.
In another apparatus for plating portions of a strip with contoured edges, a plating cell is structured to include a closely spaced pair of masking walls between which portions of the strip slide through the cell. Only portions of the strip not protected by the masking wall are subjected to treatment. In the latter example, disclosed in U.S. Pat. No. 4,224,117 to M. J. Edwards et al., an electrolyte further flows through spaces in the contoured edges of the strip to enhance plating of edge surfaces perpendicular to the length of the strip.
Both the technique of masking with a belt and that of masking with stationary walls result in treating all article portions which are conductively coupled into the electrolytic treating circuit and are exposed to the electrolyte. The result is that typically all conductive areas in a longitudinal region parallel to the direction of travel of the articles are treated.
In a strip of articles, such as back plane wiring pins or connector pins, for example, only portions of the pins in longitudinal regions along the length of the strip wherein mating connector contacts engage the pins are gold plated. In order to further reduce the use of gold, it becomes desirable, however, to limit the plating of gold of a desired thickness even within such longitudinal region to less than all four surfaces of a contact pin of typically a square cross section. This is desirable since mating contact elements typically engage only two opposite surfaces of each pin, while the two remaining pin surfaces are never contacted by a mating element.